      DOUBLE PRECISION FUNCTION X02AJF()
C     MARK 12 RELEASE. NAG COPYRIGHT 1986.
C
C     RETURNS  (1/2)*B**(1-P)  IF ROUNDS IS .TRUE.
C     RETURNS  B**(1-P)  OTHERWISE
C
C     .. Executable Statements ..
C     IN THEORY THIS SHOULD BE 2.0**(-56) BUT 2.0**(-55) HAS BEEN FOUND
C     TO BE MORE PRACTICAL IN THE PAST.
      X02AJF = 2.0D0**(-55)
      RETURN
      END
